Pulse shaping control system



Dec. 21, 1948. i R LEE. 'E A 2,456,960

PULSE SHAPING CONTROL SYSTEM Filed July 27, '1945 Current Curren! Curran z T/me I Time 77221:"

WITNESSES: lNVENTORS Re ue n Lee and Jim M P/IM/p fl. Duff} J2:

@- W BY I ATTORNE? Patented Dec. 21, 1948 UNITED STAT ES PATENT QFF LSE SHAP NTROL SYSTEM.

Reuben Lee, Linthicum Heights,..and; Philip-A Duffy, Jen, B ltimore, Md. assignorsto Westin q e ctric Co poration) East ttS nK m Ba, a corporation of Pennsylvania.

Application July 27, 1945', Serial No. 607,434

C ai Our invention relates. to current pulse shaping to be able to transform the voltage and currentv values of such pulses to different magnitudes.

from. that at which, they. are. transmitted over transmission lines from their point of generation to, the. load. they supply. However, it has been found that the. design of transformers for this purpose imposed very great difiiculties and that:

itwas in factpractically impossible to produce a transformer which would, when a rectangular voltage pulse was impressed on its primary, transmit to. almagnetron or other load a current pulse which was a true replica of the impressed pulse. Instead of yielding a flat topped pulse of the de sired. form illustrated in Fig. 2, a pulse of the form shown in Fig. 3 having an obtuse angle adjacent its beginning Edge and an acute angle at its trailing edge,-was actually produced. When; supplied to a magnetron, it was found'that pu ses, of he. F 3 crmc. produced undesir r u n y m dulatiqn. an her n si t e n: t e. magne ron ou putome re. rangement which would transmit a pulse of the type shown in Fig. 2 without distortion was accordingly much to be desired,

One object of our invention is accordingly to produce a transmission network capable of transforming the voltage and current of an impressed pulse of the rectangular type without producing substantial distortion.

Another object of our invention is to provide means for controlling the shape of the output voltage of a transformer system when a rectangular voltage pulse is impressed on its input terminals.

Still another object of our invention is to provide a network capable of transforming the magnitude of a voltage impressed on its input terminals and at the same time to produce an output pulse having vertical edges and a trough making an acute angle with the beginning-edge.

Other objects of our invention will become apparent from reading the following description taken in connection with the drawing, in which:

(Cl. .250ra-27'l Figure 1; is a schematic diagram of a transformation network for impressing rectangular current on. the anode-to-cathode circuit of a magnetron or other load,

F 2iis a time vs.- current curve showing the desired form of output pulse to be impressed bysuch a networkona magnetron,

Fig. 3 is a time vs. currentcurve showing the type. of output pulse: produced by: transformation networks of the prior art, and

Fig. 4 is a time vs. current curve showing an,

over-compensated type of "output pulse derivable in accordance with, the principles of my invention by properly proportioning the circuit constants.

Referringin; details to. Fig; l; a supply. line, which may comprise a central core- I sheath 2' is. fedi'with. energy to impress across the inductive winding 3 to which is connected a currentpulse: of: the rectangular type shown in Fig. 2. Where it is desired to step upthe amplitude ofathe-volt-age pulse to be transmitted to. the load; the conductors l and'Z are con nected: across two points a 'and' 5 of the winding 3-, of fwhich point his preferably-oneof the end terminals.- The point 4 is connected through a capacitor [Sc-shunted by a secondary winding I to the homologous endof' asecond winding-'8, preferably identical with winding 3. The free ends of the windings 3'- and 8- arerespectively connectedthrough inductors B- and i I to the respective ends ofthe cathode filament of a magnetron I2, orother-similarload. The secondary winding Tis energized by aprimary winding l0 to-supply heating current to thecathodeof magnetron l2. the magnetron l2 are preferably connected to ground. An output circuit may be coupled to a loop l3 of the magnetron l2. Capacitors l4, l5 are preferably connected between ground and the terminals of the cathode of magnetron l2.

Were the inductors 9, l I and capacitors l4, l5 omitted from the circuit of Fig. 1, an output pulse of the form shown in Fig. 3 would be impressed between the cathode and anode of the magnetron l2 when a pulse of the form shown in Fig. 2 was impressed on the input terminals 4, 5. By properly proporti-oning the inductance of the inductors 9, II, the self-inductance inherent in the windings 3 and 8, and the inductance in theleads between the cathode of magnetron I2 and such windings, to the capacitors l4, l5 and the effective capacitance of the circuit connected tothe cathode of magnetron I2, it is possible to alter the output pulse impressed between the The terminal 4 and the anode of tangular pulse shown in Fig. 2; and even to overcompensate it to the form shown in Fig. 4. Methods of determining such effective inductances and capacitances are well known to those skilled in the electrical art; specific illustrations appear in Lee Patent No. 2,412,893, filed October 21, 1943, and assigned to the assignee of this application.

The addition of the inductors 9 and H and the capacitors M and it may vary somewhat the width of the pulse applied to the magnetron. In order to keep the pulse width within practical limits, the following relationships may be adopted.

Calling L the total inductance in circuit with the cathode of magnetron i2 (i. e., L is the sum of the self (1. e., the leakage) inductance in henries of windings 3 and 8 and self-inductance of inductors 9 and H and the line wires connected to the cathode of magnetron l2); and calling C the total capacitance in farads of the same circuit (i. e., C is the sum of the effective capacitance of capacitors l4 and i5 plus magnetron capacitance plus the effective capacitance of windings 3 and 8, inductors 9 and l I, and the line wires connecting to the cathode of magnetron l2) the following relations should be fulfilled in order to produce an output pulse different from that shown Where R is the ratio of the anode-to-cathode voltage pulse impressed on the magnetron to the peak anode-to-cathode amperes through the magnetron, T is the pulse width in microseconds, K1 is a factor which may vary between the limits of 0.25 and 3.0, and K2 is a factor which may vary between 0.05 and 0.20.

The foregoing equations thus permitthe evaluation of L and C, and hence, from known data as to the self inductance and capacitance of the windings 3 and 8 and the transmission lines connecting them to the cathode of magnetron I2, permit the calculations of the inductance of inductors 9, ii and capacitors l4, l5.

When it is desired to produce an output voltage of the form in Fig. 4, the capacitors l4 and I5 should be given larger values than that corresponding to the foregoing calculations. The amount of such increase in the values of capacitors i l and lfiwill depend upon the angle of slant to be given to the trough of the voltage wave in Fig. 4.

We claim as our invention:

1. In combination with a source of substantially rectangular voltage pulses, a transformer winding having one end terminal and an intermediate terminal impressed with said pulses, a second transformer winding having an end connected to said one end by a channel offering substantially zero impedance to the frequencies embodied in 1 said voltage pulses, a load circuit having a pair of connections at one terminal, two inductors respectively connected between said pair of connections and the free ends of said windings, a pair of capacitors connected between ground and the terminals of said inductances adjacent said load, and an interconnection between said one end and the other side of said load circuit, the square root of the ratio of the total inductance in henries of the circuit connected to said pair of connections to its efiective capacitance in farads lying between the limits of 0.25 and 3.0 times the resistance in. ohms of said load circuit.

2. In combination with a source of substantially rectangular voltage pulses, a transformer winding having one end terminal and an intermediate terminal impressed with said pulses, a second transformer winding having an end connected to said one end by a channel offering substantially zero impedance to the frequencies embodied in said voltage pulses, a magnetron having its anode grounded and having a cathode with two connections, a pair of capacitors connecting the ends of said cathode to ground, two inductors respectively connected between said pair of connections and REFERENCES CITED The following references are of I record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,860,114 Okabe May 24, 1932 2,103,362 Hansell Dec. 28, 1937 2,412,893 Lee Dec. 17, 1946 

